1. Field of the Invention
The invention relates to a light emitting device, a light receiving device and a data transmission system and a data transmission method using the same.
2. Description of the Related Art
At present, most of the frequently seen data transmission techniques adopt the channel encoding technique to perform channel encoding on the information to be carried and then perform the transmission. The channel encoding is a special encoding method for preventing a channel effect from causing serious and remediless damages on the transmission signal. The main encoding schemes include a scrambler, a convolution encoder, an interleaving encoder, multi-level coding, pilot signals and mapping. The scrambler may generate a pseudo random bit sequence (PRBS) to be mixed with a two-bit signal to prevent the signal from causing the regular pattern so that the energy is over concentrated. The convolution encoder can convolute a few redundant signals and the two-bit signal to lengthen the code distance and enhance the error correcting ability during receiving. The interleaving encoder may disperse the bits in each block and exchange the bits in the block with the bits in other blocks. The purpose is to prevent the bit signal from causing the clustering phenomenon and thus to prevent the neighboring signal from causing the continuity error when being modulated. The multi-level coding, also referred to as trellis coded modulation, may optimize the encoding and modulation so that the transmission may achieve the optimum efficiency. The pilot signals with the constant level may be inserted into an OFDM signal sequence in order to perform channel estimation and error signal tracking according to the known signals so that the digital modulation becomes very perfect. As for the mapping, the channel-encoded signal may be mapped to a plurality of constellation graphs of QAM so that the FFT can perform the OFDM modulation.
However, the channel encoding technique has the high encoding complexity, needs to be combined with a lot of mathematical operations and needs to refer to the property of the channel. So, how to provide a data transmission technique, which has the low encoding complexity, does not need to be combined with a lot of mathematical operations and does not need to refer to the property of the channel, is a subject eager to be achieved.